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gutta, gt. (s); guttae, gtt. (pl)
A drop or drops.

A medical/pharmaceutical term.

The amount in a drop varies with the nature of the liquid and its temperature. It is, therefore, not advisable to use the number of drops per minute of a solution as anything more than a general guide to the amount of material being administered intravenously.

Taber's Cyclopedic Medical Dictionary; F.A. Davis Company; Philadelphia, PA; 1993.